1. Field of the Invention
The invention relates generally to the acquisition of data for analysis and control, and more specifically to a microprocessor controlled data acquisition system using a sequencer for the high speed collection of digitized data words obtained by sampling a number of analog signals.
2. Description of the Prior Art
Data acquisition systems are coupled to devices by signal lines carrying analog signals. The data acquisition systems sample the analog signals at a predetermined rate to generate a digital value of the analog signal at the time of sampling. The digital value may represent some variable, typically amplitude or frequency.
The amplitude analog signals may represent temperature or pressure velocity or even light intensity, or the analog signal representing frequency may represent vibration.
The typical data collection system may sample and analyze these signals for a number of reasons. The system may monitor the temperature of a chemical reaction to determine if safe limits are being exceeded or if the next stage of the process should be initiated. The system may monitor the change in velocity of a test crash of a vehicle to gather data to plan a better bumper design. The system may monitor the frequency of vibrations of a machine to anticipate failure. The system may monitor temperature and humidity to keep a factory within certain prescribed limits. The system may measure low light intensity varies with time as a flash bulb is used in photography.
As can be seen from these typical examples, the sampling times may vary between seconds and microseconds.
Typical systems for data acquisition used commercial microprocessors for controlling the data transfer between the analog-to-digital conversions, and the storage of the digitized data words for processing. As the need for higher speed sampling of a greater number of analog signal lines, bit slice microprocessors were designed into the data acquisition systems. Bit slice microprocessors will process the transfer of data faster than the commercial microprocessors previously used.
The bit slice microprocessor approach, however, has the limitation of being inflexible in responding to changing needs. As test conditions change on the fly, a considerable amount of software is required to adapt to the new conditions. This requires excessive time to change parameters as well as additional memory space for storing software. In addition, new conditions that must be met require that new software be written, thereby making the data acquisition not readily accessible in real time.